Self-Configuring Contact Arrays for Interfacing with Electric Circuits and Fabric Carriers

This application claims the benefit of U.S. Provisional Patent Application No. 62/666,166, filed May 3, 2018, the complete contents of which are herein incorporated by reference.

Embodiments described herein relate to smart contact arrays for detachable touch sensors, monitored displays, human-computer interaction (HCl) devices and the like that extract power from a soft circuit, which are useful for the operation of electronic textile (e-textile) circuits in a variety of articles, including without limitation garments that serve as wearable sensing devices, wallpaper in a “smart” home controlled by user-placed wall stickers, and other soft HCl surfaces comprising what are considered “soft” circuits because the nature of certain articles makes them not amenable to connection with printed circuit boards and other rigid structures during use.

In most current e-textiles, the communications interface and power electronics—including battery packs and wireless modules—are detached before the article is washed, while embedded fiber sensors, conductive traces including antennas, and small integrated circuits increasingly stay with the textile. In the case of examples involving other “soft” circuits, an item such as wallpaper may be replaced or covered over periodically with a new layer of the article. Yet a challenge exists in that, once a connector is embedded, the circuit is fixed, making it difficult for the end user to add new sensors and actuators to the e-textile. Moreover, when a connection between the electronics and the fiber sensors or traces is broken, it is difficult to repair or reestablish the connection, which in some cases renders the garment unusable.

Although not necessarily analogous, in other research areas, Open Dots, Networked Surfaces, and Smart Tables have been tried in an effort to charge or communicate with devices that are not directly aligned with a power or signal transmitter. By way of example, the Smart Table aims to locate devices placed on an active electrode grid, Networked Surfaces consist of pads and a circular array of contacts on a sliding device, and Open Dots provide an array of four contacts for device charging on an electrode grid.

However, rather than suggest a solution to the problem of communicating with a soft circuit, these approaches help illustrate the problem with wearable sensing and other soft electronics, in that they provide most of their benefits when used on printed circuit boards (PCBs) having a fixed geometry. In stark contrast, textiles, garments, wallpaper, and other articles that employ soft circuits as contemplated in the present teachings and embodiments are not as dimensionally stable as firm PCBs formed from stiff materials. Thus, if one were to try to maintain electronical connections needed for stretchable materials and e-textiles, the contact arrays in accordance with presently available technology will not remain dimensionally stable in attempting to align two deformable circuits, and the same lack of stability problem would exist when attempting to establish contact between a conventional rigid circuit and the surface of an e-textile that may shear or slip during use.

Stated differently, in the use of soft circuits, there can be no expectation to attach a multipin contact in registration from one location to the next. Another problem is that in both e-textiles and stretchable electronics applied with thin polymer films, conventional PCB fabrication methods cannot generally be used because of the low temperature tolerances such as when an article must be washed and dried. Accordingly, it is readily apparent that new materials and methods are needed for creating reconfigurable HCl systems based on soft, moving materials.

Thanks to soft electronics, new kinds of wearable and robotic systems now interact safely with the human body. Sensor skins conform to curved surfaces from aircraft wings to robot limbs. However, repair and connection methods for soft electronics lag far behind those for conventional rigid circuits. The absence of a distortion-tolerant connection technology slows innovation.

Because soft connection technology is underdeveloped, manufacturers cannot rapidly assemble soft circuits in the modular style of conventional electronics with board-to-board connectors. It's not just a prototyping problem, but a scale-up problem because in the application space of soft electronics, each product may take on a non-uniform shape. A soft circuit intended for a wearable application must conform to an individual body and may be placed at different locations by the wearer. As a sensor skin, it interacts with the environment and is likely to get damaged.

Meanwhile, a conventional circuit, for example a control board inside a digital camera, takes the same shape across millions of copies and is not likely to crash into unexpected objects inside its case. The need for repairs and revisions is low compared to a soft circuit. Yet, there are industry-standard methods to rework the conventional circuit by soldering if components fail, and to swap in parts using a flat connector cable if a sub-board fails, because PCB fabrication is a mature technology. Thanks to these established interconnect methods, it is far easier to prototype, deploy, repair, and revise a conventional circuit than a soft one, illustrating how the right system of connector materials and methods would be transformative for soft electronics.

Another part of the connection and repair problem is thermal compatibility. Polymers in soft electronics are incompatible with soldering. Conventional printed circuit board (PCB) electronics fabrication and rework sends whole circuits through an oven at 260 C, where most polymers will flow or burn. The soldering problem is not new. It also affects glass screens in liquid crystal displays and flat flexible cables printed on low-cost polyester. A microstructured elastomer connection industry formed in the 1970s, and those technologies are still used by the soft electronics community today. Researchers have only recently added low-temperature materials and methods including ultrasonic bonding, liquid metal contacts, and aerosol metal deposition.

Some exemplary embodiments herein include self-configuring circuits suitable for use with HCl applications that employ wired sensors and actuators, and which avoid or limit the need for power plugs, wires, and the like. Exemplary circuits may comprise a contact array providing a physical interface configured to extract power from a power source, such as but not limited to lithium ion microbatteries, for an electronic device in contact with a larger underlying circuit such as an e-textile or wallpaper, without needing any alignment. A contact array of some present embodiments may output the maximum and minimum voltages at its contacts and provides startup power for a randomly-placed battery-less sensor, conductive trace, patch, or other conduit for electricity to HCl devices or like materials in soft electronics.

An exemplary contact array may be configured and utilized to obtain power for itself by tapping into a surface having positive and negative voltage traces at unknown locations with respect to the contacts of the array.

Besides wearable technology, there is a broad arrange of applications for embodiments described herein, including without limitation a smart home controlled by user-placed wall stickers, a biochemical sensor monitoring a wound for signs of infection and attached to a patient-worn electronic textile (e-textile) garment, as well as actuators controlled by transmitted command signals. User-configurable e-textile circuits of exemplary embodiments may further be accompanied by novel methods for repairing large-area flexible circuits. In accordance with present embodiments, an Example is described involving a 7×7 contact array suitable for use on various kinds of soft articles with electronic surfaces and circuitry.

An advantage of some present embodiments over conventional conducting materials such as conducting wallpaper that use special patterns of pin spacing on a device, is that unlike the conventional materials, exemplary embodiments may be configured to be amenable to variable placement of the pins and continual power and/or communication signal transmission even if the underlying circuit stretches and no longer has the original pattern prescribed to match the power circuit to the device that must receive the power.

Some embodiments comprise a distortion-tolerant connector/patch is based on a grid of independent electrical contacts. An exemplary patch uses a large array of contacts, each connected to at least one or a pair of diodes or transistors and a pass-through signal connector. This configuration is capable of delivering DC voltages and AC signals to the patch. It may become more powerful as the contact density increases. At high enough density, and on a flexible or stretchable substrate, the structure may resemble anisotropic conductive tape usable in the thin LCD display industry, except with the added ability to send signal, power, and ground to different destinations.

A fabrication challenge exists to maximize the number of independent contacts to the soft electronic surface while also making room for power and signal traces plus supervisory microcontrollers on the connector patch. This challenge may be addressed by a combination of springy microelectromechanical (MEM) contacts with a fabric mesh. These thin-film devices are highly resilient.

An aspect of some embodiments is a modular system where soft circuits may be patched together, simplifying construction and repair of large-area wearables and skins.

The disclosed fiber based carrier materials with attached grippers may contribute to electronic textiles (E-textiles), a rapidly emerging field. Smart materials may be incorporated into E-textiles by embroidering, knitting, weaving, spinning, braiding, coating/laminating, printing and chemical treatments. Mechanical tangling at the microlevel adds a new tool to the E-textiles suite. An exemplary approach uses micro-origami with numerous applications including biomedical devices, energy storage systems, optoelectronics, MEMS, metamaterials, bendable microclectronics, and origami nanorobots.

According to an aspect of some embodiments, devices may be made from thin, flexible films with meandering paths that bend instead of break when stretched. The structures may be transferred to porous, fiber-based carrier materials instead of silicone. Indeed photodiodes, sensors, and other integrated semiconductor devices may all be transferred and attached to porous fiber supports according to exemplary embodiments herein, for a wide variety of applications. Fabrics offer lightweight mechanical support and high conduction of air and fluids, an advantage for wearable sensors, though the contact region is non-uniform compared to a cast silicone film. For this reason, mechanical tangling may be used to adhere MEMS devices onto fabric carriers as opposed to adhesion and other printing based methods which would be difficult to control when transferring thin film devices from wafers to fabrics. Strain-engineered microfabricated grippers may be wrapped around a textile mesh during a final step in a microfabrication process. Applications include but are not limited to sensor integration into breathable structures like tissue engineering scaffolds, bandages, and filters.

Three-dimensional out of plane structures have previously been produced as coiled cantilevers, nano-scrolls and tubes through micro and nano-origami, in which mismatched tensile and compressive stresses in bilayers are employed. Differential thermal expansion or a lattice size mismatch between layered materials can cause released bimorphs to curl uniformly from the substrate. The magnitude of the force, elastic moduli, and the thickness of the film may be controlled to decide the curvature of the bilayer objects. The direction of rolling or folding of the patterns may be controlled by stresses, shape, and direction of etching. Adhesion forces and collision with other objects can change the shape of the structures—an expected outcome when the grippers interact with fabric fibers. In the present work, mechanical tangling between thin-film devices and fiber materials is achieved by strain-mismatched bilayer curling. Exemplary grippers are producible from thin-film bilayers on a silicon wafer. At the final release step, the grippers curled up and interacted with fabrics.

Mechanical grippers may be used to bring electronic contacts from one side of a mesh to the other, which is difficult to do on continuous thin films of other soft materials like silicone or polyimide. Some embodiments use mechanical strain to produce large arrays of redundant grippers from planar thin-film designs. MEMS grippers may be used to make reliable electrical contact with conductive fibers integrated with or inserted into fabrics.

1 FIG. 100 102 102 102 102 shows circuitrythat harvests external power to in turn power, for example, an HCl deviceor other e-textile. Merely for simplicity of illustration, deviceis illustrated as being a load and an output, here an LED. In practice, devicemay conceivably be of any of a wide variety of circuitry configurations or devices. The devicemay be on-board electronics such as programmable modules connectable via soft circuit.

102 100 101 101 102 101 101 103 101 101 104 Besides device, the circuitrycomprises electrical contact array. The electrical contact arraymay also be independent of devicebut for a power connection being established between them. The electrical contact arraycomprises a plurality of external contacts 1, 2, 3, 4 . . . N (which in some embodiments may be identified as “pins”). The electrical contact arrayfurther comprises a plurality of power collection diodesor transistors, at least one or at least two per external contact, configured to extract power from a power source. The electrical contact arrayfurther comprises signal pass-throughs for passing communication signals (in contrast to power signals). In addition, electrical contact arraycomprises a power output (here, output terminals) configured to output the maximum and minimum voltages to which the contacts 1, 2, 3, 4 . . . N are exposed.

101 102 The electrical contact arrayobtains power for itself and the connected circuitby contacts 1, 2, 3, 4 . . . N that are configured for tapping into a power circuit surface having positive and negative voltage traces, but which are at unknown or otherwise variable locations concerning their positioning with respect to the contacts 1, 2, 3, 4 . . . N.

2 FIG. 2 FIG. 101 210 201 202 203 204 101 210 201 203 202 204 101 201 202 203 204 illustrates an electrical contact arraycollecting and distributing power from an underlying power circuitwith positive and negative voltage traces,,, and. The contact arraymay be placed or positioned randomly on the underlying circuit. The underlying power circuitmay comprise a surface with exposed interdigitated electrodes. Inthe tracesandare positive contacts and the tracesandare negative contacts. Contact arraymay be placed or positioned randomly with respect to the power circuit traces,,,, etc. such that some of the contact pins do not contact any power circuit trace. Contact pin 3, for example, is non-conducting in the illustration as it did not come into contact with any underlying power trace, at least not for the position illustrated.

1 FIG. 210 102 102 201 202 203 204 101 210 illustrates an embodiment in which each contact pin 1, 2, 3, 4 . . . N is connected to two diodes and a pass-through. The diodes (in contact with an underlying trace) produce a rectified power signal while maintaining electrical isolation between positive and negative traces of the underlying power circuit. In turn, the pass-throughs transmit any communication signals originating from the surface of the HCl deviceor being transmitted to the device. Though traces,,, andhave been identified as power traces in this particular illustration, any one or more of the traces may be configured instead as a communication signal terminal. The configuration of contact arrayas illustrated makes the device equipped to work with a wide variety of underlying circuitsirrespective of certain differences in arrangement and positions of power traces and communication signal terminals/traces. The contact array is self-configuring in that irrespective of the position or placement of the contact array with respect to the underlying circuit, it can still collect and conduct power and communication signals from the underlying circuit.

2 FIG. 101 102 To prevent shorting, the contact pins 1, 2, 3, 4 . . . N involved in power collection should be narrower than the smallest gap on the power circuit. Each pin is pointy (narrow) so it cannot touch two different traces at once and short them together. The pin spacing, however, may be bigger than the smallest gap on the power circuit. With random alignment, some of the pins might not contact a power circuit trace, an example being pin 3 in. The contact arraymust span at least one positive and one negative trace (and preferably more if there is a possibility of defects and distortion in the underlying power circuit) to ensure that the on-board electronics ofsuch as programmable modules connectable via soft circuit will receive power. In some embodiments, transistors may be used in place of diodes. Transistors are made using the same materials and processing techniques as diodes, and they can enable a signal from a supervisory microcontroller to turn on (closed circuit) or turn off (open circuit) the conductive path from the contact pin to the device. Materials and processing techniques are employable to transfer working diodes and spring contacts to a fabric surface.

An example of contact spacing in the exemplary contact array is 4 mm. Other suitable spacing distances may include but are not limited to 10 mm or smaller, 9 mm or smaller, 8 mm or smaller, 7 mm or smaller, 6 mm or smaller, 5 mm or smaller, 4 mm or smaller, 3 mm or smaller, 2 mm or smaller, 1 mm or smaller, at least 1 mm, at least 2 mm, at least 3 mm, at least 4 mm, or some combination of these qualifications. Small surface mount packages and automated assembly equipment may be used to reduce the pin spacing below 4 mm. Moreover, certain levels of miniaturization may be achieved by making the contact array directly from thin film semiconductors. For example, thin films of silicon and other semiconductors, which bend because of their thinness. This prevents the material from exceeding the breaking strain during bending. Thin semiconductor films can be integrated directly into flexible articles for a conformal contact array using the novel arrangements described herein.

A number of applications in HCl devices become readily apparent with the use of the smart contact arrays of present embodiments. These include, but are not necessarily limited to: electrical connections for user-positioned sensors on wallpaper, tablecloths or other soft HCl surfaces; repair “materials” enabling a non-expert user to identify and reconnect broken traces on a large-area HCl circuit; connectors for human activity sensors on materials that otherwise might distort the pin pattern due to stretching, a problem likely to be encountered in a variety of settings especially clothing but which is suitably addressed by present embodiments which do not require dimensional stability or rigid PCBs as with conventional approaches.

In the case of human activity sensors such as biosensors for pulse, blood pressure or other vital signs, an exemplary contact array may collect analog signals from passive sensor elements built into the surface of the biosensor. The contact array or a further circuit in connection therewith may then digitize the collected analog signals and transmit them for monitoring a condition of a subject. Further, it is contemplated that through the practice of some present embodiments, a number of lightweight, repositionable sensors in a single article such as a garment with wearable sensing technology may be provided which draw power from a shared external battery pack.

Contact arrays of the present embodiments are suitable for use in powering electrodes that measure, for example, muscle signals and resistive strain sensors made from knit conductive threads. To this end, PCT/US19/15520, filed Jan. 29, 2019, and United States Provisional Patent Application 62/623,078 (“Stretchable Optical Fibers for Strain-Sensitive Textiles”), filed Jan. 29, 2018, describe example systems in which present embodiments may be employed. The complete contents of PCT/US19/15520 and U.S. App. No. 62/623,078 are incorporated herein by reference. When tracking muscle activation sequences with sensors, a one-size-fits-all approach fails given that each individual has well-defined anatomical landmarks that are unique from person to person. Thus, the unmet need for spatial customization is one of the problems currently limiting the adoption of smart athletic garments, but which can be successfully addressed through the use of flexible and stretchable substrates in accordance with the current embodiments.

An embroidered interdigitated electrodes pattern on fabric would be suitable to power a smart contact array dropped into a pocket and provide the device secure wired connections to sensors embedded in sports medicine wearables and other biomedical wearable sensors.

3 FIG. 4 FIG. 2 FIG. 302 301 302 302 401 302 401 shows a configuration that includes an embroidered patternof the fabric in contact with a contact array. The patternis completed with conductive thread (e.g., silver-plated nylon thread). In simulated testing, the embroidered electrode patternwith the geometries described above was supplied with 0 and 5V.is shows contact array and e-textile circuitcollecting power from interdigitated electrodeswhich are arranged as shown schematically in. The circuitmay be made from conformal materials, for example.

301 401 The contact arrayis an example of a rigid contact array with the physical and electrical configurations described herein, whereas the contact arrayis flexible and may also be stretchable. Embodiments may comprise body-conforming arrays with flexible and stretchable substrates. Such flexible and stretchable embodiments may be achieved using the same principles described here with thin film semiconductor materials and using photolithography and conventional microfabrication techniques.

Some embodiments comprise a patch comprising a contact array, with the patch being configured for repairing circuits even if those circuits being repaired were not designed expressly to run a contact array. In this arrangement, the contact array is configured to tap into an operating electronic textile that carries a power line and ground line sparsely over the circuit area. When the contact array rests across these signal and power lines, it can extract power for the on-board electronics of an e-textile article.

In some embodiments, the contact array is made from a thin material that conforms to the surface of a circuit. Conformal contact array embodiments may be configured to patch a broken power line (or lines) and inject power or signals into a different part of the underlying circuit of a given article.

Applications from the present embodiments include other HCl devices, for example those which are configurable by an end user. Through the teachings provided herein, power could be provided to a smart home control system based on a user attaching switches, sliders and small displays to a large-area wallpaper that has electronic traces built in. In this application, the smart contact array would let the user power small devices at any position on the wall, and with any orientation.

Contact array pin shape may vary among embodiments. It was found that pins of a slight saddle shape were less reliable for consistent contact between contact array and underlying power circuit. In some embodiments the contacts may be spring contacts.

302 3 4 FIGS.and To achieve certain performance metrics (e.g., reliability of connectivity) a power circuit may be configured to be particularly suited to a contact array or vice versa. However, the two elements may be implemented independent of one another and yet be compatible. What is desirable in exemplary applications is for the underlying power circuit to have an arrangement that, on average, will put some of the contacts of the contact array on a positive trace and others on a negative trace. It will be appreciated that interdigitated positive and negative electrode arrays likeofmay be described using just two parameters: the electrode width and the electrode gap. The contact array should be configured such that the contact array's contact pins are narrower than the smallest gap between traces on the power circuit.

A method of harvesting power from a power circuit that has positive and negative voltage traces may be described as follows. A first step may comprise randomly positioning a contact array with respect to the power circuit traces such that some of the contact pins do not contact any power circuit trace, the contact array comprising contact pins that are narrower than the smallest gap between traces on the power circuit. A second step is outputting the maximum and minimum voltages to which the contacts are exposed.

5 6 FIGS.and 5 FIG. 6 FIG. 5 FIG. 5 FIG. 5 FIG. 6 FIG. characterize performance variations based on different pairings of electrode width and electrode gap for an interdigitated power surface.is a graph of electrode width (Y-axis) against electrode gap/pin spacing (X-axis) with color coding to indicate favorability based on the minimum number of contacts (worst-case scenario) to the A or B net over all positions and all rotations of a 7×7 contact array with 49 contact points.reproducesand accompanies it with additional images aroundproviding illustrations of the electrode array and interdigitated electrodes at different positions plotted in. In, the black dots represent pins that do not make contact with either the A or B electrode.

5 FIG. 5 FIG. It will be appreciated that closely-spaced electrodes like those in the top left ofprovide the greatest assurance that a contact array will find power irrespective of the position or placement of the contact array with respect to the power circuit electrodes. That said, larger power electrode gaps create space in the layout for other electrodes that carry communication signals instead of power. Therefore, some embodiments may employ layouts like the one in the lower right offor self-configuring applications that undergo changes in positioning, such as occurs with a garment being worn or when a sensor is repositioned, and which need to communicate over the surface.

If signals outside an expected power range are to be used, distortion may be mitigated by active switching. A changing voltage detected at a microcontroller pin while other pins remained at 0 or 5V would indicate a signal (rather than sliding of the whole array). The signal pin may then be disconnected from the power-collection circuit using transistors. When used in a battery-free contact array, this active approach may depend upon a passive contact array to initially power up the onboard electronics.

Some embodiments comprise or consist of distortion-tolerant connectors for soft electronics. Some embodiments apply microscale semiconductor components to fabrics to solve the problem of electrically connecting two soft circuits with unknown contact locations. An exemplary embodiment is a conformal patching diode array.

Stretchable electronics may comprise materials that can stretch to produce considerable distortion.

7 FIG. illustrates a problem introduced by stretchable electronics: electrical contact distortion in materials that can stretch. Some stretchable electronics may comprise silicones, which may stretch 4× or greater beyond their original length. Some stretchable electronics may comprise hydrogels, which may stretch beyond 10× their original length.

7 FIG. 701 702 703 704 701 702 701 702 703 704 shows two circuitsandwhich have matching contact arraysandrespectively (each a 2×6 array in this illustrated example). Circuitsandmay be two rigid circuits. With two rigid circuits, after two points on the surface ofare located and aligned with two points on the surface of, every contact pad in the arrayis aligned with every contact pad in array.

701 702 701 701 702 703 704 703 704 7 FIG. 7 FIG. Circuitsandmay alternatively be flexible and/or stretchable circuits. As a simple non-limiting example, a stretchable circuitmay comprise a Spandex fabric substrate with a soft circuit contact pad made from silver ink, inkjet printed onto the Spandex fabric. In stretched states, the circuits are labeled as′ and′ respectively. When connecting to a stretchable circuit, there is no guarantee things can ever be aligned, especially if one of the circuits is already installed on a curved surface., at figure bottom, shows an attempted connected of the arraysand. Even under a best fit, it is not possible for all contacts of the two arraysandto contact one another. Some contact pairs have large contact areas, some small contact areas, and some no contact at all because the distorted contact shapes cannot align. The latter case is marked a with small “x” in each instance in.

8 FIG. 800 701 702 800 800 800 701 702 800 shows a soft electronic patchsolving the distorted contact problem. The soft circuits′ and′ under the patchsupply power and ground to the patch. The patchtransmits or receive signals that need to be linked across the soft circuits′ and′. An exemplary soft electronic patchcomprises an array of microelectromechanical system (MEMS) contacts, means for routing signals and power to a supervisory circuit, and a porous fiber-based carrier.

800 800 210 101 800 703 704 802 802 703 704 802 800 800 2 FIG. 8 FIG. 8 FIG. A soft electronic patchmay comprise a textile with integrated semiconductor components and large arrays of redundant, springy electrical contacts. The redundancy means that only some of the electrical contacts need to make an electrical connection with an underlying circuit for the patchto operate as expected. (Recall contact 3 from, which did not need to contact the underlying circuitfor the contact arrayto work as intended.) When a patchis placed in contact with a distorted pad arrayor, the pad routes signals and power to a supervisory circuit(though twelve supervisory circuits are illustrated in, only one is explicitly labeled for clarity of illustration). The supervisory circuitmay be a supervisory microcontroller and multiplexer that scans the contacts in its neighborhood and encodes the information in a serial stream.shows analog data collection between contact terminals of arraysand, and serial data connections among the supervisory circuits. A patchmay comprise small microcontrollers in large modular arrays. Fabrication of a patchmay comprise applying aerosol metal coatings, including metal traces, in 3-D printed sockets for the supervisory circuits (which may be microcontrollers).

800 An exemplary patchincludes a porous fiber-based carrier that makes through-surface electrical connections possible. An important distinguishing feature of a textile platform is the high porosity of fabric compared to the thin solid polymer or elastomer films used in most other soft electronics research. The fabric structure permits electrical contacts to run from the contact side to the other side of the connector patch without etching or drilling. Fabric construction methods may also incorporate fine wires directly in the textile to carry signals.

800 800 Though an exemplary patchmay be well suited for use with soft circuits, it may also be employed in connecting hard circuits or a combination of soft and hard circuits. Exemplary patchesmay, for example, be used with textiles and microfabricated silicon devices.

The contacts of exemplary contact arrays and patches may comprise strain-engineered micromechanical grippers configured to mechanically entangle with fabric carriers and provide adherence of MEMS devices to the fabric carrier.

9 FIG. 9 FIG. 901 902 902 904 905 906 907 shows a variety of alternative grippers with arm lengths in the range of 200 microns. Non-limiting examples of gripper configurations include clasp, square clasp, cross, log/cross-bar, triangle clasp, claw, and claw with hooks. Exemplary non-limiting dimensional examples are shown inas well.

The radius of curvature for reliable clasping depends on the fabric being clasped. Exemplary non-limiting fabrics may have fibers in the 50 to 100 micron diameter range. The reciprocal of radius of curvature for a released gripper arm of uniform width is given by,

1 2 1 2 1 2 Equation (1) reduces to equation (2), if both layers have same biaxial moduli. In the above equation, ρ is the radius of curvature, d=d+d, combined thickness of two layers, n is the ratio of the elastic modulus of the two layers (E/E) and m is the ratio of their thicknesses, (d/d), ε is the strain mismatch given as follows,

10 FIG. where σ is the biaxial stress, ν is the Poisson's ratio, E is the elastic modulus. The choice of the thickness of upper metal layer in the bimorph greatly affects the radius of curvature. From equation (1), with a SiO2 layer thickness of 400 nm, and other parameters as listed in Table 1, the plot ofis obtained showing radius of curvature versus thickness of upper metal layer.

TABLE 1 Properties of an exemplary bilayer for grippers Elastic Measured Measured Calculated Modulus Poisson's Thickness Residual Stress Radius Material (GPa) Ratio (nm) (MPa) (microns) Cr Metal E= Metal v= 130 Metal σ= 160 ± 5 142 ± 5 140 0.21 (tensile) Oxide Oxide E= Oxide v= 400 Oxide σ= − 71 0.2 300 ± 25 Oxide E= (Compressive) 83

11 11 FIGS.A toF 11 FIG.A 11 FIG.B 11 FIG.C 11 FIG.D 11 FIG.E 11 FIG.F illustrate an exemplary method for fabricating grippers and attaching them to a textile carrier.shows a thermal oxide deposition on a silicon substrate. In, a predetermined resist pattern is produced with photolithography.shows metal (e.g., chromium) deposition which may be by sputtering.shows metal lift-off in solvent. Next inare steps of wafer dicing and oxide etching using the metal as a mask. Atfabric fibers are tightly attached over the chips and silicon is etched (e.g., by xenon difluoride) through the fibers, releasing the gripper structures. Partial release, leaving grippers tethered to the wafer at their centers, may be achieved by reducing the number of etch cycles.

11 11 FIGS.A-F 12 12 FIGS.A toC Whileshows a single fiber in a cross-sectional view,illustrates a perspective view of grippers transferring semiconductor payloads to a fabric swatch, creating a porous structure with mechanical strength coming from fibers and functionality from thin-film devices. The alignment of fibers and grippers may be random or controlled.

12 FIG.A 11 FIG.E 12 FIG.B 12 FIG.C 1201 1202 1206 1203 1204 1205 corresponds closest with; a 2D thin film strain-mismatched bilayer has been fabricated but remains flat and attached to a wafer substrate. The illustrated patterns includes an array of redundant microelectromechanical system (MEMS) contactswith gripper arms, conductive metal tracesfor routing signals and power to a supervisor circuit, and a plurality of supervisor circuitseach arranged at a respective node. Exemplary conductive traces are meandering paths, which when subject to moderate forces are able to distort instead of breaking. The supervisor circuits may each include a power rectifying circuit, such as a diode pair. In, the thin film pattern has been positioned adjacent to a fabric carrierand the bilayer (including the conductive top layer of the 2D thin film and the bottom layer) is released from the substrate. The release from the substrate and inherent tensile properties of the gripper arms cause the arms to curl about the adjacent fibers of the fabric carrier. Transferring the microfabricated structures to fabrics via secure mechanical joints may require fiber wrapping, preferably more than halfway around in at least some embodiments.shows remaining substrate being removed, leaving only the array of MEMS contacts, conductive traces, and the porous fiber-based carrier. The resulting structure has a dense array of electrical contacts on one side, and rectifying devices with connector wires on the other.

904 906 901 902 905 9 FIG. 9 FIG. 9 FIG. For the materials and thicknesses in Table 1, it was found that structure lengths of 200 microns and greater are sufficient for hooking on polyester and nylon woven and knit fabrics having fiber diameters in the 50- to 100 micron range, and having mesh openings in the 500 micron to 1 mm diameter range. Features such as crossbars (in) and a “crab claw” (in) spanned more of the fiber surface; devices that rely on contact area for adhesion may include such features at the ends of the grippers. The three “clasp” designs (,, andin) were too short (<200 microns) to surround these fibers at the ˜150 micron radius of curvature. However, such configurations may suit differently sized and configured fibers. Individual gripper specifications may also among embodiments, including but not limited to arm length. As mentioned previously, fabrication may entail intentional fiber alignment with gripper contact arrays. Alternatively, positioning may be random. If alignment is not possible, increased gripper density may be used to help ensure a strong bond between a thin film device array and a fabric.

13 FIG.A 13 FIG.B 13 FIG.C 14 FIG.A 14 FIG.B 14 FIG.C 14 FIG.B 14 FIG.D is a photograph of arrayed MEMS grippers transferred to a fabric mesh.is a photograph of an individual MEMS gripper.is an electron micrograph of a gripper seen from the contact side of the material, just after transfer from a silicon substrate.is an electron micrograph of a gripper successfully attached to woven polyester fabric.is an electron micrograph of a gripper successfully attached to a knit nylon fabric.is zoomed view of themicrograph, showing secure clasping of 50 micron diameter fibers by the “crab claw” design.is an optical micrograph of a knit nylon fabric showing interaction between polymer fibers and bilayer materials.

Some embodiments comprise fabricating silicon diodes then releasing them from the surface without damaging the devices. This suspended air isolation method is rarely seen now, but its predecessor was one of the earliest approaches (pre-1960s) toward electrical decoupling of semiconductor devices fabricated on a single substrate.

11 11 12 12 FIGS.A-F andA-C Silicon diodes may be defined by ion implantation in an oxidized silicon-on-insulator device layer, followed by the MEMS gripper process (e.g., see) modified to make electrical contact with the terminals of each diode through an additional etch step before metallization. Diodes will be nearly freed from the substrate by back-etching from the underside with a deep reactive ion etch (a process which may also be used to make fiber-alignment holes), then completely released from the front side in a brief XeF2 silicon etch at the same time the MEMS grippers are released onto aligned fabrics.

Patch-to-surface electrical contact area may be increased by aerosol printing a conductor onto the tips of released devices to increase their conductive surface.

In a prototypical embodiment, this circuit was formed as a sandwich between two PCBs, with the contacts made by soldering 1/16 inch (1.6 mm) diameter brass spheres to 1 mm diameter via using solder paste. Between the two boards, diodes (from STMicroelectronics, Geneva, Switzerland, manufacturer part number TMMBAT48FILM) were soldered on end, two per contact point. The pass-throughs were made from 0 ohm resistors (Vishay Intertechnology, Inc., Malvern, Pennsylvania). All components were in mini-MELF format. The assembly was run through a reflow oven to finish bonding the spheres and components to the pads on both sides of the board. The top side of the board was equipped with an emitting diode (LED) and a pair of contacts for sampling the rectified voltage, with a via providing a test point for each pass-through signal.

Contact spacing in the exemplary contact array was 4 mm. The power electrodes were 3 mm in width with a gap of 2 mm between electrodes. The embroidered pattern of the fabric in contact with the array was completed with conductive thread array (silver-plated nylon thread). In simulated testing, the embroidered electrode pattern with the geometries described above was supplied with 0 and 5V. Tests were carried out by lifting and placing the device at a new position. The red LED indicated a successful circuit with no open-circuit errors in 100 different placements with the array horizontal and 5 errors in 100 placements at 45 degrees.

Here, an e-textile circuit made from woven strips of conductive fabric was driven with 5V via contact with the 7×7 array. Illumination of the LED, while the contact array rested on the two active traces of the conductive fabric, demonstrated providing power extraction to a soft circuit.

To validate these findings related to power collection, a function generator, outputting a sine wave, was connected to the pass-through resistor on a pin that was not contacting 5V potential or a grounded electrode. This setup represented a pin touching a signal trace. The output was compared to the original sine wave signal on an oscilloscope, showing results consistent with power being extracted to the soft circuit.

5 FIG. 6 FIG. It will be appreciated that interdigitated positive and negative electrode arrays can be described using only two parameters: the electrode width and the electrode gap. Accordingly, an interdigitated electrode surface was used to simulate the number of contacts over a continuous range of electrode widths, and gaps, in units of contact pin spacing, in order to determine the sufficiency of the contact array to extract and distribute power (or transmit signals) even while its positioning changes relative to the underlying circuit. The results of the simulation are shown graphically in, with additional results provided in the outer images shown in.

5 FIG. For simulating rotation, the electrodes and contact array underwent computer-simulation modeling for angles between 0 and 90 degrees, and center position ranging from the center of one electrode, to the center of the neighboring gap. Because of symmetry for a 7×7 array, this range covers all possible array positions with respect to the electrode pattern. In the simulation, computer code translated and rotated the 7×7 array over the interdigitated electrode pattern, keeping track of the lowest number of pins touching the positive and the negative net (whichever was least) during all the positions and orientations. In the interdigitated pattern, a net consists of every other electrode, denoted inas the “A” or the “B” net.

6 FIG. 5 FIG. 6 FIG. 6 FIG. The “scores” represented inare the least number of pins contacting either of the two nets at all positions. If, at any position, a configuration was found that made no contact to either one of the nets, that electrode width/gap combination received a score of 0. The graph of(center image in) shows a complex boundary to the “safe” zone of electrode configurations that provide more than one or two contacts at the worst case position. However, there is a solid zone of higher numbers (more reliable contact) as the electrode gap is made smaller and as the electrodes are made wider than one pin-spacing unit. The black dot best seen inmarks the configuration used in experiments on an embroidered interdigitated circuit.

5 FIG. Interdigitated electrode patterns at the lower left corner of the contiguous safe zone (for example, a relative width of 1 and electrode gap of 0.1) should be able to stretch with respect to the pin spacing and still power the onboard circuit at any orientation, as long as the growing widths and gaps do not cross into the red zone in the graph of. The dimensions of the array and contacts present differing parameters as shown by the materials as listed in Table 2. The first row under the headings is for the demonstration device, and the bottom row is for a potentially smaller system adaptable to curved surfaces, a PCB surface with a ball grid array (BGA) device.

TABLE 2 Limits on device dimensions in two materials systems Maximum pin Minimum Minimum pin System width electrode gap spacing E-textile/ 1 mm spring pin ~1.5 mm   ~2 mm PCB diameter PCB/BGA 0.3 mm ~0.5 mm ~0.6 mm

6 FIG. 5 FIG. 5 FIG. The interdigitated electrodes performed nearly without errors as expected based on their location on(center portion, corresponding withgraph, black dot). At 45 degrees, the few errors were connected to the underlying electrodes having a slight saddle shape, leading to non-contact of the diagonal rows at some positions. This problem may be remedied by using spring contacts or by making the array from conformal materials. In view of the above descriptions, it will be appreciated that closely-spaced electrodes like those in the top left ofprovide the greatest assurance that the circuit will find power. However, a larger electrode gap creates space in the layout for other electrodes that carry signals instead of power.

5 FIG. 5 FIG. Therefore, layouts like the one in the lower right ofmay be preferable for some self-configuring applications that undergo changes in positioning, such as occurs with a garment being worn or when a sensor is repositioned, and which need to communicate over the surface. Of course, a larger array than the 7×7 array described here would provide a path to more complex underlying circuits. In this regard, even the worst case at the top right of the graph, with its large electrode gaps, would consistently touch both power nets and provide power if it were a 10×10 instead of 7×7 array. While a larger device area is part of the balance that must be reached in that it has potential drawbacks for miniaturization, the prospect exists to push the viable area of the plot inout to larger-sized electrode gaps, thus making room for sensor communication lines.

11 11 FIGS.A toF 2 Following is a specific fabrication example in agreement with, described generally above. A 400 nm thick thermal oxide was grown on silicon wafers by wet oxidation in a tube furnace at 1000 C. Standard photolithography and etching were used to pattern Cr metal into the predetermined designs. To produce the metal thickness and stress values in Table 1, a sputtering machine (Lesker PVD75) was used to sputter coat the wafers from a Cr target using 300 W DC power, 5 mTorr argon pressure and 15-18 minutes of deposition time. By depositing metal at below 200 C on a silicon dioxide (SiO) layer grown at 1000 C, strain mismatched bimorphs were created. The oxide was removed by plasma etching everywhere except where it was protected by the metal pattern. For achieving this, wafer dices were processed in a March plasma etcher for 10 minutes with 240 mTorr pressure of CF4:H2 at a partial pressure ratio of 60:40 and a RF power of 260 W.

2 2 Fabrics (Matte Tulle Fuschia 100% nylon, Casa Collection Chiffon Chocolate 100% polyester, Glitterbug Micronet Fabric White 100% nylon, Jo Ann Fabrics) were attached tightly over the surface, then the structures were released using a XeFetch chamber (Xactix, Inc.) to undercut them from the wafer by a 10 micron deep isotropic silicon etch. For grippers with arm widths in the range of 15 microns, the etch process required 30 or more 30 s cycles of exposure to an atmosphere of 3 Torr XeFfor complete release. The upper metal film constrains the expansion of the lower SiO2 layer; thus when released from the substrate, the bilayer curls with a radius of curvature that minimizes its potential energy.

The present example used radial arrays of gripper arms with lengths in the 200 micron range. Other curvature radii possible include 60-100 microns.

14 14 FIGS.A toD Scanning electron microscopy and optical microscopy were used to evaluate the radius of curvature, as well as whether MEMS devices could realistically be moved from silicon wafers to fabrics using the strain energy based “pop-up” process. Film stress was measured on 4-inch diameter wafers using a Toho film stress monitor. The properties in Table 1 (a 400 nm oxide, and a 130 nm thick Cr layer) produced structures with a radius of curvature ranging from 100 to 193 microns, for an average of 144±41 microns based on measurements from 6 structures. For the fabric transfer process, imperfections included missed connections, too-short grippers, and crushing of grippers by misaligned fabric. Successes showed that the fabric is neither visibly damaged nor does the fabric interfere with MEMS processing ().

The embodiments described herein are non-limiting and are meant to be exemplary. Accordingly, it will be understood that the embodiments described herein are not limited in their application to the details of the teachings and descriptions set forth, or as illustrated in the accompanying figures. Rather, it will be understood that the present embodiments and alternatives, as described and claimed herein, are capable of being practiced or carried out in various ways. Also, it is to be understood that words and phrases used herein are for the purpose of description and should not be regarded as limiting. The use herein of such words and phrases as “such as,” “comprising,” “e.g.,” “containing,” or “having” and variations of those words is meant to encompass the items listed thereafter, and equivalents of those, as well as additional items. The use of “including” (or, “include,” etc.) should be interpreted as “including but not limited to.”

All descriptions herein, including those incorporated by reference, are meant to illustrate, rather than to serve as limits on the scope of what has been disclosed herein. It will be understood by those having ordinary skill in the art that modifications and variations of these embodiments are reasonably possible in light of the above teachings and descriptions.